At present, with the development of mobile communication technology, the short message service has become a popularized service ranked second in frequency of use of all mobile communication services, because of the low expense and convenience in communication. Many value-added services, such as weather forecast and information delivery, of operators are increasingly introduced by taking the advantages of short message.
Therefore, the importance of the function and method of storing the short message to the mobile terminal is self-evident. The memory of mobile terminal itself can store short message. Nonetheless, because a Subscriber Identity Module (SIM) card has the unique feature of being replaceable and pluggable, users prefer to store short message in the SIM card.
According to requirement of the GSM11.11 specification, the structure of the 6F3C file of the currently used SIM cards, which is used for storing short message, is the linear fixed-length file. It means that the record length of each short message of the 6F3C file is fixed. However, in practice, data lengths of short messages are different. If space is reserved for each short message according to a fixed length, then the actually reserved space cannot be fully utilized because of different data length of each short message, thereby reducing the number of short messages actually stored in limited storage space, and inevitably wasting resources.